#include<stdio.h>
int main()
{
	int grade=0;
	while(scanf("%d",&grade)!=EOF)
	{
		if(grade>=90 && grade<=100)
		printf("A");
		else if(grade>=80 && grade<=89)
		printf("B");
		else if(grade>=70 && grade<=79)
		printf("C");
		else if(grade>=60 && grade<=69)
		printf("D");
		else if(grade>=0 && grade<=59)
		printf("E");
		else 
		printf("Score is error!");
		
	}
	return 0;
}
